Stacking the electronic members on the support makes it possible to obtain an electronic module that is relatively compact.
A method is already known in the state of the art for soldering together at least two stacked elements forming a stack, the method being of the type in which a laser is directed onto an end face of the stack so that the laser heats the stack, and at least one parameter of the laser is adjusted.
As a general rule, and the laser parameter is a parameter selected from an irradiation duration, a surface area of the end face of the stack that is irradiated by the laser, and an irradiation power of the laser.
By way of example, the stack comprises a support constituting a printed circuit (first element of the stack) and a semiconductor chip (second element of the stack). A solder-forming mass is interposed between these two elements.
The stack is characterized by certain thermal features, in particular the critical temperature of the semiconductor chip above which the chip is destroyed, and the melting temperature of the solder, which temperature must be lower than the critical temperature of the semiconductor chip.
In general, each parameter of the laser is adjusted in empirical manner to a value such that: firstly a maximum temperature reached by the stack does not exceed the critical temperature of the semiconductor chip; and secondly the maximum temperature reached by the stack is greater than the melting temperature of the solder-forming mass.
Thus, for a stack comprising only two elements, the value for each parameter of the laser can be adjusted empirically because the number of thermal characteristics of the stack that need to be taken into account is limited.
However, the number of thermal characteristics that need to be taken into account increases with the number of elements in the stack.
Consequently, when the stack comprises at least three elements, an empirical adjustment of the parameter value is unlikely to take account of all of the thermal characteristics of the stack, and can lead to the soldering between two of the elements of the stack being of relatively poor quality, or else to one of the elements in the stack being damaged.